Two-stage process for hydrodenitro-genization of naphtha



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F.G REFORM ERG/A5 IN V EN TOR.

AGENT L. P. EVANS Filed May 28, 1959 O E T I. P T ma is of AY N 5 65ANMA MT 0 .T A N C P c m G l n m h .J. WA B 8 w 5 6 2/ v m 9 dmflhzdlrmZ0 Oct. 10, 1961 TWO-STAGE PROCESS FOR HYDRODENITROGENIZATION OF NAPHTHATO CONTAMlNANT RECDVEQY AND OR, REF'lNER-f FUEL. MAN? la/ J\ UnitedStates Patent 3,003,053 TWO-STAGE PROCESS FOR HYDRODENITRO- GENIZATIONOF NAPHTHA Louis P. Evans, Woodbury, N.J., assignor to Socony Mobil OilCompany, Inc., a corporation of New York Filed May 28, 1959, Ser. No.816,412 7 Claims. (Cl. 208-254) The present invention relates to thepretreatment of hydrocarbon mixtures to remove sulfur and/or nitrogenand, more particularly, to the treatment of petroleum oil fractions toremove nitrogen.

It has been known for several years that it was advantageous to removesulfur and/or nitrogen from mixtures of hydrocarbons containing organiccompounds containing sulfur and/or nitrogen prior to contacting thehydrocarbon mixture with a catalyst subject to at least partialdeactivation by either sulfur or nitrogen compounds. It has been foundadvantageous to remove sulfur from mixtures of hydrocarbons for thepurpose of reducing corrosion in subsequent operations. Thus, in 1929British Patent No. 315,439 issued in which the patentees described thetreatment of hydrocarbons in the presence of metallic sulfide attemperatures within the range of 392 to 572 F. The so-treatedhydrocarbons, it was disclosed, can be readily employed in othercatalytic processes, such as catalytic hydrogenation, and poisoning ofthe catalyst avoided.

In 1935 British Patent No. 424,531 issued in which the p'atenteesdisclosed that Frequently in the produc tion of valuable liquidhydrocarbons, in particular knockproof motor fuels and valuablelubricating oils by refining, destructive or aromatizing hydrogenationunder pressure at temperatures of 572 to 1022 F., injurious deposits areformed which apparently result from a content of highly unsaturatedhydrocarbons, in particular diolefins, or of resins or asphalts in saidinitial materials.

The patentees recommend that the mixture be hydrogenated underconditions such that only the unsaturatedconstituents are hydrogenatedand that the pretreated product be subjected to refining, including aprocess in which sulfur containing impurities are decomposed andremoved, destructive or aromatizing hydrogenation or cracking at ahigher temperature than that employed in the pretreatment. 'As catalystsfor the hydrogenation these patentees recommend metal compounds of thesecond to the eighth groups of the periodic system, for example, oxides,phosphides, nitrides, in particular sulfides for example of molybdenum,tungsten, chromium, vanadium, manganese, cobalt, nickel, iron, zinc,rhenium, uranium, tin or mixtures of these and the like.

When the industry reformed only straight run naphthas the sulfur andnitrogen content thereof presented no problem. That is to say it is arelatively simple operation to reduce the sulfur content of straight runnaphtha to twenty parts per million (20 p.p.m.) and to simultaneouslyreduce the nitrogen content to less than one part per million 1 p.p.m.).However, the reduction of sulfur and nitrogen to acceptable levels forreforming over aplatinum-catalyst when pretreating a mixture ofhydrocarbons such as coker gasoline containing for example 1 percent ofsulfur and 400 p.p.m. of nitrogen presents a more diffcult problem.

For example, a mixture of hydrocarbons containing 650 p.p.m. of sulfurand not more than about 10 p.p.m. of nitrogen can be treated under theconditions set forth in Table I to produce 21 treated mixture ofhydrocarbons containing 20 p.p.m. of sulfur and not more than 1 p.p.m.of nitrogen.

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TABLE I Catalyst:

3.3% by weight C00. 16.1% by weight M00 on alumina.

S.c.f./b. is standard cubic feet per barrel.

Under the same conditions employing the same catalyst the nitrogencontent of a mixture of hydrocarbons containing 15 p.p.m. of nitrogencannot be reduced to one p.p.m. However, by reducing the space velocityand/or by increasing the pressure, the rate of circulation of hydrogen,and/or the temperature, the nitrogen content of a mixture ofhydrocarbons containing 15 p.p.m. of nitrogen can be reduced to not morethan one p.p.m. On the other hand, many units now used for thepretreatment of naphthas to be reformed over platinum catalyst weredesigned for the relatively low pressure of say 500 p.s.i.g. and therelatively high space velocities and relatively low rates of hydrogencirculation which have been found to give satisfactory reductions in thesulfur and nitrogen contents of straight run naphtha. Consequently, theindustry must either build additional equipment for the specialtreatment of high-nitrogen stocks or operate at reduced space velocitiesand reduced throughput.

Another solution of the problem is to use platinum catalyst for theremoval of nitrogen. Platinum is an excellent catalyst for the removalof nitrogen. Thus, for example, the nitrogen content of a mixture ofhydrocarbons containing 15 p.p.m. of nitrogen can be reduced to 0.2p.p.m. by contact with platinum catalyst under the same conditions asset forth in Table I. However, such a platinum catalyst costs about fiveto fourteen times the cost of a satisfactory cobalt-molybdenum catalyst.

It has now been discovered that, while under the relatively mildconditions given in Table III a cobalt-molybdenum catalyst will reducethe nitrogen content of a mixture of hydrocarbons from 15 p.p.m. to 1.6p.p.m. and a platinum catalyst under the same conditions will reduce thenitrogen content of a mixture of hydrocarbons from 15 p.p.m. to 0.2p.p.m., the nitrogen content of a mixture of hydrocarbons can be reducedfrom 15 p.p.m. to 0.5 p.p.m. by contacting the mixture of hydrocarbonsfirst with a cobalt-molybdenum catalyst and then with a platinumcatalyst under'the conditions set forth in Table II.

7 TABLE II Tons of catalyst/ 10,000 b ll Pressure, psi g 400 to 500Temperature, "F 650 to 800 Space velocity, v./hr./v 2 to 5 Circulationrate of hydrogen, s.c.f./b 500 to 1000 It is another object of thepresent invention to provide a method of hydrodecontarninating a mixtureof hydrocarbons containing organic compounds of nitrogen comprisingfirst contacting said mixture with a catalyst comprising a mixture ofoxides and/or sulfides of cobalt and molybdenum and then with a catalystcomprising platinum-group metal on alumina wherein the volume of thecatalyst comprising oxides and/or sulfides of cobalt and molybdenum isat least equal to, and not more than about ten times, the volume of thecatalyst comprising platinum-group metal on alumina. It is a furtherobject of the present invention to provide a method ofhydrodecontaminating a mixture of hydrocarbons containing organiccompounds of nitrogen which comprises contacting said mixture first witha catalyst comprising a mixture of oxides and/ or sulfides of cobalt andmolybdenum and then with a catalyst comprising platinum-group metal onalumina wherein the oil to be hydrodecontaminated is contacted with atotal amount of both catalysts at a rate not exceeding about 10 to 30tons per 10,000 barrels of said mixture per day i.e., at an overallliquid hourly space velocity in the range of about 5.5 to about 1.83,and wherein the volume of the catalyst comprising oxides and/ orsulfides of cobalt and molybdenum is about one to about three times thevolume of said catalyst comprising platinum-group metal on alumina. Itis also within the scope of the present inven tion to provide a methodof hydrodecontaminating a mixture of hydrocarbons containing organicnitrogen compounds which comprises contacting said mixture first with anon-noble metal catalyst having hydrogenating, hydrodesulfurizing andhydrodenitrogem'zing capabilities and then with a catalyst comprising ametal of the platinum group of the eighth group of the periodic table onalumina wherein the oil to be hydrodecontaminated is contacted with atotal quantity of both catalysts at the rate of about 10 to about 30tons per 10,000 barrels of said hydrocarbon mixture per day i.e., at anoverall liquid hourly space velocity in the range of about 5.5 to about1.83, and wherein the volume of said non-noble metal catalyst is atleast equal to, and not more than ten times, the volume of said platinumgroup catalyst. Other objects and advantages will become apparent tothose skilled in the art from the following description taken inconjunction with the drawing in which FIGURE 1 is a flow sheet showingthe flow of liquid and gases employing a single reactor and two staticbeds of catalyst.

At the outset it must be emphasized that passage of a mixture ofhydrocarbons containing organic nitrogen compounds successively throughtwo beds of catalyst as described hereinafter results in a reduction inthe nitrogen content of the mixture of hydrocarbons which is more thanjust the additive effect of the two beds of catalyst. This is manifestfrom an inspection of the data presented in Table III.

TABLE HI Feed (boiling range100 F. to 400 F.)

Nitrogen, pp in 15 Sulfur, p.p m 650 Olefins, vol. percent 4 Conditions:

Tons of catalyst per 10,000 h./d 11 Pressure, p si 5: 425 Temperature, F690 Liquid hourly space velocity, v./hr./v Rate of circulation ofhydrogen, s.c.f./b 500 Case I Case II Case III avolumes Catalyst A B A+1volume B Hydrodecontaminated Product:

Nitrogen, p.p.m 1. 6 0. 2 0. 5 Nitrogen removed, p.p.m 13.4 14. 8 l4. 5Sulfur, ppm 20 20 20 Sulfur removed, percent 97 97 97 Catalyst A3.3weight percent 000; 16.1 weight percent M00 on the cobalt-molybdenumcatalyst alone less 25% of the nitrogen removed by the platinum catalystalone. That is 15 p.p.m. (feed) minus 75% of 13.4 p.p.m. less 25% of14.8 ppm. is 1.25, and greater than 0.5 ppm. Therefore, it is apparentthat the two catalysts when used as described hereinafter work togetherto produce a result that is not merely the additive effect of each.

In accordance with the principles of the present invention a mixture ofhydrocarbons generally containing not more than about 20 p.p.m. ofnitrogen is contacted successively with a non-noble metal catalyst,preferably sup ported on alumina, having hydrogenating,hydrodesulfurizing and hydrodenitrogenizing capabilities, and with aplatinum-group metal catalyst, preferably supported on alumina.Illustrative of the non-noble metal catalyst are the variouscobalt-molybdenum catalysts comprising about 0.8 to about 3.0 percent byweight of cobalt and about 2.0 to about 16.5 percent by weight ofmolybdenum as oxides and/or sulfides and the balance alumina.Illustrative of the platinum group catalysts are catalysts comprisingabout 0.01 to about 2.0 percent (preferably 0.3 to 0.6) by weightplatinum, up to about 2.0 percent by weight of chlorine and/ or fluorinesupported on alumina. The mixture of hydrocarbons to behydrodecontaminated is contacted with about 10 to about 30 tons ofcatalyst per 10,000 barrels of mixture of hydrocarbons per day of whichabout 50 to about percent is the non-noble metal catalyst and about 10to about 50 percent, preferably about 20 to 30 percent, is platinumgroup catalyst. Reaction conditions for hydrodecontaminating a mixtureof hydrocarbons containing not in excess of 20 ppm. of nitrogen toproduce a decontaminated product containing not more than 1 ppm. ofnitrogen are given in Tables IV and V wherein the non-noble metalcatalyst is fifty percent by volume of the total volume of catalystcharged to both reaction zones.

TABLE IV First reaction zone Catalyst:

3.3 wt. percent C00 16.1 wt. percent M00 Balance alumina Broad PreferredPressure, p.s.i.g 400 to 800 400 to 500 Temperature, F 500 to 800 650 to800 Space Velocity, v./hr./v 2 to 8 2 to 5 Circulation Rate of Hydrogen,s.c.f.,lb 300 to 3,000 500 to 1,000

TABLE V Second reaction zone Catalyst 0.6 wt. percent Pt 0.6 wt. percenthalogen Balance alumina Broad Preferred Pressure, p.s.i.g 400 to 800 400to 500 Temperature, F 500 to 800 650 to 800 Space Velocity, v./hr./v 2t0 8 2 to 5 Circulation Rate of Hydrogen, s.c.f./b. 300 to 3, 000 500 to1, 000

In the drawing is illustrated a typical flow diagram of a meansemploying a static bed of non-noble metal catalyst superposed on astatic bed of platinum-group metal catalyst for reducing the nitrogencontent of a hydrocarbon mixture for use as a feed to a reactionemploying a nitrogen sensitive catalyst, i.e., a catalyst which is reversibly or irreversibly poisoned by nitrogen compounds. (A reversiblepoisoning is one in which the activity of the catalyst can be restored.An ireversible poisoning is one in which the activity of the catalystcannot be restored by known means.) Typical of a catalyst which ispoisoned by contact with nitrogen compounds are the platinum reformingcatalysts presently used. It has been found that platinum reformingcatalysts lose activity at an intolerable rate when reforming mixturesof hydrocarbons, such as naphtha, containing more than 1 p.p.m. ofnitrogen. Accordingly, a naphtha to be reformed on Contact with aplatinum reforming catalyst must have a nitrogen content not in excessof 1 p.p.m. if the onstream time of the reforming catalyst is to be ofpractical duration. Furthermore, it is manifest that, even though thepresent method of hydrodenitrogenizing a feed to a reaction in which anitrogen-sensitive catalyst is used is at least 95 percent efiicient,i.e., removes at least 95 percent of the nitrogen, there is a maximumconcentration at which the present method will produce a feed having therequired nitrogen content of not more than a given p.p.m. Consequently,the nitrogen content of the feed to a hydrodenitrogenizing process suchas described herein cannot exceed about 20 p.p.m. when a pretreatedprodnot containing not more than 1 p.p.m. of nitrogen must be produced.However, when the nitrogen-sensitive catalyst used in a subsequentoperation has a nitrogen tolerance greater than 1 p.p.m. the feed to thepretreating operation can be proportionately higher. Accordingly, thefeed to the pretreater must contain not more than B -C p.p.m. of mtrogenwhere Nitrogen Removed O.a- 1 100 B=maximum p.p.m. nitrogen tolerated inpretreater product =maximum p.p.m. of nitrogen in feed to pretreaterSince generally about 95 to about 96 percent of the nitrogen in anaphtha feed is removed by the method of the present invention it ismanifest that the feed to the pretreater disclosed in the presentinvention must not exceed about 20 to about 25 p.p.m. in order toproduce a feed for a subsequent catalytic reaction containing not morethan 1 p.p.m. of nitrogen.

Nevertheless, mixtures of hydrocarbons containing more than of nitrogencan be treated provided a mixture of hydrocarbons is available as adiluent. The diluent can be a material which is inert in the subsequentcatalytic reaction and later removed as by distillation or a materialwhich is to be subjected to the same subsequent catalytic reaction inconjunction with the mixture having the excessive nitrogen content.Thus, for example, an undiluted coker naphtha containing 140 p.p.m. ofnitrogen cannot be treated under the conditions set forth hereinafter toprovide a reformer feed containing 1 p.p.m. of nitrogen. On the otherhand, in most refineries the volume of straight run naphtha to bereformed is usually 'a multiple of the volume of coker naphtha to bereformed. Consequently, the straight run naphtha can be used as adiluent. Thus, a coker naphtha containing the concentration of nitrogenshown in Table VI can be diluted with a straight run naphtha in theratio of to 95 volumes of straight run naphtha to 95 to 5 volumes ofcoker naphtha to provide a pretreater feed containing not more than ofnitrogen from which a reformer feed containing not more than 1 p.p.m. ofnitrogen can be produced.

TABLE VI Ooker Naphtha Straight Run N aphtha Pretreater Percent Productor Feed N0. Nitrogen Reformer p.p.m. Parts p.p.m. Parts Removed Feed.

of Niby Volof Niby Volp.p.m. trogen ume trogen ume Nitrogen Toillustrate the method of the present invention reference is made to thetreatment of a mixture of coker naphtha containing p.p.m. of nitrogenand a straight 11in naphtha containing 1 p.p.m. of nitrogen inproportions to provide a mixture containing about 20 p.p.m. of nitrogen.

A mixture of coker and straight run naphtha containing about 20 p.p.m.of nitrogen is drawn from a source not shown through pipe 1 by pump 2and discharged into pipe 3 at a pressure greater than that in reactor11. The naphtha mixture or pretreater feed flows through pipe 3 to heatexchanger 4 where the pretreater feed is in indirect heat exchangerelation with the effluent of reactor 11. From heat exchanger 4 thepretreater feed flows through pipe 5 to heat exchanger 6 where thepretreater feed is in indirect heat exchange relation with the effluentof reactor 11 flowing thereto through conduit 14 from reactor 11. Fromheat exchanger '6 the pretreater feed flows through pipe 7 to coil 8 inheater 9.

In heater 9 the pretreater feed is heated to reaction temperature withinthe limits of about 500 toabout 800 F., preferably about 650 to about800 F. The heated pretreater feed'fiows from heater 9 through conduit 10to reactor 11. At some point in conduit 10 intermediate to heater 9 andto reactor 11 hydrogen or hydrogen-containing gas such ashydrogen-containing gas flowing from a reformer (not shown) throughconduit 35 is mixed with the heated pretreater feed in the proportion ofabout 500 to about 1000 standard cubic feet of hydrogen per barrel ofpretreater feed. As indicated the hydro gen-containing gas can besupplemented with gas from other sources introduced into conduit 3-5through conduit 32.

The mixture of pretreater feed and hydrogen, now designated chargemixture, flows downwardly in contact with a static bed of non-noblemetal catalyst, e.g., a mixture of oxides of cobalt and molybdenum on analumina support through the first reaction zone 12. The efliuent offirst reaction zone 12 comprising feed naphtha, hydrogen derivatives ofsulfur and nitrogen, i.e., hydrogen sulfide and ammonia, unhydrogenatedorganic sulfur and nitrogen compounds and hydrogen enters the secondreaction zone 13 wherein the first reaction zone efiluent contacts astatic bed of platinum-group metal catalyst, e.-g., platinum on alumina.The first reaction zone efiiuent flows downwardly through secondreaction zone 13 to the outlet thereof. (Those skilled in the art willrecognize that reaction zones 12 and 13 can bein separate reactors.)

From reaction zone 13 the effluent therefrom flows through conduit 14 toheat exchanger 6 Where the chinent from reaction zone 13, designatedfinal effluent, is in indirect heat exchange relation with thepretreater feed as described hereinbefore, From heat exchanger 6 thefinal efliuent flows through conduit 15 to heat exchanger 16 where thefinal effiuent is in indirect heat exchange sure the lowest boilinghydrocarbon to be further catalytically treated is condensed. Forreformer feed, the temperature of the final eiiiuent is reduced to atemperature at which C and heavier hydrocarbons are liquid at theexisting pressure. From cooler 19 the condensed and uncondensed finalefiiuent flow through conduit 20 to liquid-gas separaotr 21.

In liquid-gas separator 21 the uncondensed final efiiuent, in theillustrative case the C and lighter hydrocarbons, hydrogen, and volatilehydrogen derivatives of contaminants, sulfur and nitrogen insoluble inthe condensed final eflluent at the temperature and pressure existing inliquid gas separator 21, separates from the condensed final efiiuent andfiows through conduit 22 to conduit 36 and thence to the refinery fuelmain and/or recovery of the sulfur and ammonia by known means. Thecondensed final effluent, hereinafter designated condensate, flowsthrough pipe 23 to the suction side of pump 24. Pump 24 discharges thecondensate into pipe 25 through which the condensate flows to heatexchanger 26. In heat exchanger 26, the condensate is in indirect heatexchange relation with the bottoms of stripper 29 flowing therefromthrough pipe 39. From heat exchanger 26 the condensate flows throughpipe 27 to heat exchanger 16 where the condensate is in indirect heatexchange relation with the reactor effluent fiowing from heat exchang er6 through conduit 15 as described previously. From heat exchanger 16 thecondensate flow through pipe 28 to stripper 29. Stripping gas such ashydrogen-containing gas flowing from a reformer (not shown) throughconduit 37 under control of valve 38 is introduced into stripper 29 inany suitable manner to provide intimate contact between the strippinggas and the condensate under conditions of temperature and pressure toremove substantially all of the volatile hydrogen derivatives of thecontaminants.

The stripping gas, in this instance hydrogen-containing gas, flows fromstripper 29 through conduit 30 to compressor 31 and thence throughconduits 32 and to conduit 10 where it is mixed with the pretreater feedin the proportions disclosed hereinbefore to make the charge mixture.When the supply of hydrogen-containing gas is sufiicient to meet thedemands for the hydrogenation of the pretreater feed and for strippingthe condensate without cycling the strippers overhead to reactor 11, thestripper overhead flows through conduit 33 under control of valve 34 toconduit 36 where it is mixed with the gas from separator 21.

The stripped condensate containing not more than innocuousconcentrations of catalyst poisons in the illustrative case not morethan 1 ppm. of nitrogen, flows from stripper 23 through pipe 39 to heatexchanger 26 where the stripped condensate, i.e., stripper bottoms, isin indirect heat exchange relation with the condensate flowing fromseparator 21 through pipe 25 as described hereinbefore. The stripperbottoms flows from heat exchanger 26 through pipe 40 to the charge pumpof the subsequent operation (reforming in the illustrative case) or tostorage.

From the foregoing description of the method of the present inventionfor hydrodecontaminating a mixture of hydrocarbons to be contacted witha catalyst sensitive to a contaminant in said mixture of hydrocarbonswhich contaminant reacts with hydrogen in the presence fo ahydrogenating catalyst to form volatile hydrogen derivatives of saidcontaminants those skilled in the art will understand that the method ofthe present invention comprises contacting a mixture of hydrocarbonscontaining a contaminant of the class defined in a concentration notgreater than where B is the innocuous concentration in ppm. of thecontaminant and On is the percent of said contaminant remaining afterthe hydrodecontamination in the presence of hydrogen and a non-noblehydrogenation catalyst having hydrodecontaminating capabilities in afirst reaction zone, contacting the effluent of said first reaction zonecomprising hydrogen and unreacted compounds of said contaminant with aplatinum-group metal catalyst, and separating volatile hydrogenderivatives of said contaminant from the treated hydrocarbons of saidhydrocarbons mixture to obtain a hydrocarbon mixture as feed for asubsequent reaction in the presence of a contaminant-sensitive catalystcontaining not more than innocuous concentration of said contaminant,said non-noble catalyst being used in volume at least about equal to,but not greater than about ten times, the volume of said platinum groupcatalyst and the total volume of both catalysts being not more thanabout 30 tons per 10,000 barrels of said hydrocarbon mixture treated perday,

I claim:

1. A method of hydrodenitrogenizing naphtha which comprises charging afirst reaction stage with particleform solid non-noble metalhydrogenating catalyst having hydrdenitrogenizing capabilities, charginga second reaction stage with particle-form solid platinum-group metalhydrogenating catalyst having hydrodenitrogenizing capabilities, thetotal amount of said catalysts charged to said first and second reactionstages being in the proportion of about 10 to about 30 tons per 10,000barrels of feed per day, the aforesaid non-noble metal catalyst beingabout 50 to about percent by volume and the aforesaid platinum-groupmetal catalyst being the balance to make percent by volume of theaforesaid about 10 to about 30 tons, passing feed containing at least 15ppm. of nitrogen comprising naphtha containing more than 15 ppm. ofnitrogen and a diluent successively through said first and secondreaction stages to obtain an effluent of which the C and heavierhydrocarbons boiling in the naphtha range contain not more than 1 p.p.m.of nitrogen whilst maintaining a pressure in the range of about 400 toabout 800 p.s.i.g., a temperature in the range of about 500 to 800 F.,and a hydrogen circulation of about 300 to about 3,000 standard cubicfeet of hydrogen per barrel of said feed, in each of said first andsecond reaction stages maintaining in said first reaction stage a liquidhourly space velocity in the range of about 2 to about 11 and in saidsecond reaction stage a liquid hourly space velocity of about 4 to about55 dependent upon the liquid hourly space velocity in the said firstreaction stage and the volume of catalyst in said second stage, andseparating from the aforesaid effluent a C and heavier hydrocarbonfraction boiling in the naphtha range containing not more than 1 p.p.m.of nitrogen.

2. The method set forth in claim 1 wherein the nonnoble metalhydrogenating catalyst is about 70 to about 80 percent by volume of theabout 10 to about 30 tons per 10,000 barrels of feed per day.

3. The method set forth in claim 1 wherein the diluent is naphthacontaining not more than 1 ppm. of nitrogen.

4. The method set forth in claim 1 wherein the nonnoble metalhydrogenating catalyst is selected from the group consisting of amixture of oxides of cobalt and molybdenum on alumina support, and amixture of oxides and sulfides of cobalt and molybdenum on aluminasupport.

5. The method set forth in claim 4 wherein the platinum-group metalhydrogenating catalyst comprises about 0.3 to about 0.6 percent byweight of platinum and up to about 2 percent by weight of halogenselected from the group consisting of chlorine and fluorine on aluminasupport.

6. The method set forth in claim 1 wherein the nonnoble metalhydrogenating catalyst comprises about 3.3 percent by weight of oxide ofcobalt, about 16.1 percent by weight of oxide of molybdenum and thebalance alumina, wherein the platinum-group metal hydrogenat- 9 ingcatalyst comprises about 0.6 percent by weight of platinum and about 0.6percent by weight of chlorine on alumina support, wherein the feedcomprises thermally cracked naphtha and straight run naphtha andcontains more than 15 but not more than about 31 ppm. of nitrogen,wherein the temperature in both stages is in the range of about 650 toabout 800 F., wherein the pressure in both stages is in the range ofabout 400 to about I 500 p.s.i.g., wherein the liquid hourly spacevelocity in the first stage is about 2 to about 5, and wherein thehydrogen circulation is about 500 to about 1,000 standard cubic feet ofhydrogen per barrel of feed.

7. The method set forth in claim 6 wherein the nonnoble metalhydrogenating catalyst is about 50 percent by volume.

References Cited in the file of this patent UNITED STATES PATENTS

1. A METHOD OF HYDRODENITROGENIZING NAPHTHA WHICH COMPRISES CHARGING AFIRST REACTION STAGE WITH PARTICLEFORM SOLID NON-NOBLE METALHYDROGENATING CATALYST HAVING HYDRDENITROGENIZING CAPABILITIES, CHARGINGA SECOND REACTION STAGE WITH PARTICLE-FORM SOLID PLATINUM-GROUP METALHYDROGENATING CATALYST HAVING HYDRODENITROGENIZING CAPABILITIES, THETOTAL AMOUNT OF SAID CATALYST CHARGED TO SAID FIRST AND SECOND REACTIONSTAGE BEING IN THE PROPORTION OF ABOUT 10 TO ABOUT 30 TONS PER 10,000BARREL OF FEED PER DAY, THE AFORESAID NON-NOBLE METAL CATALYST BEINGABOUT 50 TO ABOUT 90 PERCENT BY VOLUME AND THE AFORESAID PLATINUM-GROUPMETAL CATALYST BEING THE BALANCE TO MAKE 100 PERCENT BY VOLUME OF THEAFORESAID ABOUT 10 TO ABOUT 30 TONS, PASSING FEED CONTAINING AT LEAST 15P.P.M. OF NITROGEN COMPRISING NAPHTHA CONTAINING MORE THAN 15 P.P.M. OFNITROGEN AND A DILUENT SUCCESSIVELY THROUGH SAID FIRST AND SECONDREACTION STAGE TO OBTAIN AN EFFLUENT OF WHICH THE C5 AND HEAVERHYDROCARBONS BOILING IN THE NAPHTHA RANGE CONTAIN NOT MORE THAN 1 P.P.M.OF NITROGEN WHILST MAINTAINING A PRESSURE IN THE RANGE OF ABOUT 400 TOABOUT 800 P.S.I.G., A TEMPERATURE IN THE RANGE OF ABOUT 500* TO 800*F.,AND A HYDROGEN CIRCULATION OF ABOUT 300 TO ABOUT 3,000 STANDARD CUBICFEET OF HYDROGEN PER BARREL OF SAID FEED, IN EACH OF SAID FIRST ANDSECOND REACTION STAGES MAINTAINING IN SAID FIRST REACTION STAGE A LIQUIDHOURLY SPACE VELOCITY IN THE RANGE OF ABOUT 2 TO ABOUT 11 AND IN SAIDSECOND REACTION STAGE A LIQUID HOURLY SPACE VELOCITY OF ABOUT 4 TO ABOUT55 DEPENDENT UPON THE LIQUID HOURLY SPACE VELOCITY IN THE SAID FIRSTREACTION STAGE AND THE VOLUME OF CATALYST IN SAID SECOND STAGE, ANDSEPARATING FROM THE AFORESAID EFFLUENT A C5 AND HEAVIER HYDROCARBONFRACTION BOILING IN THE NAPHTHA RANGE CONTAINING NOT MORE THAN 1 P.P.M.OF NITROGEN.